<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>title</title>
<script defer src="main.js"></script></head>
<body>
    <div id = 'title'>
        <button  class="btn btn-primary" type = 'primary'>按钮</button>
    </div>
</body>
</html>